This invention relates to an extremely small and flexible flow guided balloon catheter for use in small and tortuous blood vessels in body organs such as the brain or kidney for diagnostic angiography.
Catheters have long been used for various purposes. One of the earliest types was the drainage catheter. These instruments were relatively large and stiff and presented no great problems either in manufacture or in manipulation in use. Later, vascular catheters were developed for use in the large veins and arteries. These also were relatively large in diameter and stiff enough to be advanced through a blood vessel by pushing on the proximal end. When such catheter was equipped with a balloon, it was not difficult to include a separate balloon inflation lumen in the catheter tube in addition to another lumen or lumens for diagnostic or treatment purposes.
More recently, flow guided catheters were developed having a balloon on the distal end which could be inflated to pull the catheter along by the flow of blood in an artery or vein. Such catheters had to be very flexible, but as long as they were used in the major veins and arteries they could still be large enough in diameter to accommodate a balloon inflation lumen, in addition to whatever lumens were required for diagnostic or treatment purposes. Thus, the use of the diagnostic angiography catheter as a therapeutic tool is becoming well accepted.
The conventional form of construction, however, is not capable of the size reduction necessary for use in the small and tortuous arteries in certain organs, such as the brain or kidney. And even if conventional catheters could be scaled down still further in size, other problems arise. The double or multiple lumen system becomes impractical because resistance to flow of fluid through a lumen increases inversely as the fourth power of the radius of the lumen, with a given length and fluid viscosity.
For the purpose of diagnostic angiography, it is necessary to inject a contrast agent or occluding material beyond the balloon. The lumen conveying such material must be of sufficient diameter to deliver the material at the distal end of the catheter within acceptable pressure limitations. This cannot be done in a double or multiple lumen system when the catheter tube is of very small diameter.
Objects of the invention are, therefore, to provide an improved catheter for diagnostic angiography, to provide an improved flow guided catheter for use in small and tortuous blood vessels, to provide a balloon catheter in which a material injected into a blood vessel is utilized to inflate the balloon and to provide a single lumen balloon catheter having a calibrated leak for injection.